Synthesis of Pyrano[3,2‑c]pyrazol-7(1H)‑one Derivatives by Tandem Cyclization of 2‑Diazo-3,5-dioxo-6-ynoates (Ynones)

The construct of the core of pyrano­[3,2-c]­pyrazol-7­(1H)-one derivatives is realized. The key step includes a tandem cyclization, namely, a metal-free cascade 6-π electrocyclic ring closure-Michael reaction of 2-diazo-3,5-dioxo-6-ynoates (ynones). The cascade reaction cleanly generated the desired products in excellent yields under mild conditions.